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10.3.3 Sanitation System Maintenance
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10.3.3 Sanitation System Maintenance

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All wastewater systems whether they are individual household systems or centralized village wastewater systems require routine inspections to determine the condition and maintenance requirements of the system.

 

Wastewater Treatment System

 

General operation and maintenance requirements on different systems refer to Chapter 4 – Rural Wastewater Treatment Technologies and Chapter 5 – Wastewater Treatment Process Design. The specific operation and maintenance requirements will be outlined in the O&M manual prepared by the contractor, and the O&M requirements will depend on the type, size, and complexity of the system.

 

Sewage Collection System

 

The O&M requirements of the sewage collection system will depend on the design, type and complexity of the collection system. A simple gravity flow system with sewers that are installed with good fall or slopes (generally over 1% to 2%) will likely not require frequent cleaning. However, low gradient sewers with interceptor tanks will normally require more frequent inspections and cleanings. Sewer cleaning should be scheduled on a regular cycle, for example, 100 percent of the sewer lines should be cleaned every three to five years or approximately 20% to 30% of the sewer lines should be cleaned every year (Arbour and Kerri, 1998).

 

In some instances, the sewage collection system includes pump stations and forced main sewers, which requires more frequent inspections, cleaning and maintenance activities. Pump stations can be complex and the operators who maintain them should be skilled. There are generally two levels of maintenance associated with wastewater pump stations: (1) routine inspection, and (2) mechanical and electrical maintenance.

 

The purpose of routine inspection is to monitor and assess the operation of the pump station. An inspection usually involves a variety of tasks, such as verifying control system operation, observing electrical and mechanical equipment for signs of abnormal operation, performing preventive maintenance tasks (such as cleaning the pump), and recording operational information. Inspection verifies that the pump station is operating as intended and that there are no existing or impending problems that will affect pump station operation and reliability.

 

The purpose of electrical/mechanical preventive maintenance is to maintain the integrity of the mechanical and electrical systems to keep the station operating reliably and/or to restore the system components to their original condition and functionality. Pump stations have numerous electrical components including electrical motors, controls, protective devices such as circuit breakers and overloads, wiring systems, lighting, heating, and ventilation. Electrical preventive maintenance should be performed at scheduled intervals based either on running time (for example every 2,000 hours of operation), or by calendar (once every three months, for example). Scheduled repairs and replacement of both electrical and mechanical equipment are also part of the preventive maintenance program. Certain components of electrical and mechanical equipment (such as wear rings, mechanical seals, packing, and pump impellers) are subject to wear and require periodic inspection and replacement. Overload relays on electrical equipment need to be inspected and replaced periodically. Electrical motors require periodic overhauls. Scheduled maintenance is also necessary on force main isolation, air and vacuum relief valves.

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